1. Field of the Invention
The invention relates to a driving control apparatus and a control method for a vehicle. More particularly, the invention relates to downshifting control when a vehicle is coasting with a throttle valve being fully closed.
2. Description of the Related Art
A driving control apparatus for a vehicle is known which includes (a) an engine which generates power by fuel combustion, (b) a transmission which changes engagement/disengagement states of plural frictional engagement devices so as to realize plural speeds whose gear ratios are different from each other, and (c) a coasting time disengagement restricting device for maintaining a high speed side frictional engagement device in an engagement state until a low speed side frictional engagement device obtains a predetermined torque capacity at the time of automatic downshifting of the transmission when the vehicle is coasting with a throttle valve of the engine being fully closed. For example, a driving control apparatus for a vehicle disclosed in Japanese Patent Laid-Open Publication No. 11-287317 is known (refer to claim 6, and FIG. 7). When a predetermined fuel cut condition including a condition that the vehicle is coasting is satisfied, fuel supply to the engine is stopped (fuel cut is performed) for enhancing fuel economy, which is widely adopted. An example of such a driving control apparatus for a vehicle is disclosed in Japanese Patent Laid-Open Publication No. 9-53718.
However, in the above-mentioned driving control apparatus for a vehicle, in the case where downshifting of the transmission is output when fuel cut is performed during coasting, and the high speed side frictional engagement device is maintained in the engagement state by the coasting time disengagement restricting device, when fuel cut is cancelled by an accelerator operation or the like and fuel supply is restarted, problems may occur that an input rotational speed of the transmission is hindered from increasing due to engagement of the high speed side frictional engagement device, which results in an occurrence of shift shock and an increase in the shifting time.